Fikedever
Honestly, Fen doesn't need to worry about the banners and advertisements in his page IMO. All he has to do is warn people that he's planning on ditching Patreon in the near future in favor of Sub.Star and as an extra incentive he can re-introduce the content he removed due to Patreon policies, plus expand on it. That alone will make people jump over.
Innoxia (the developer of Lilith's Throne) was using Patreon for funding as well (and making well over 2.5k a month) but when the platform started getting all high-and-mighty and telling her to cut her game she basically told them to fuck off and switched to Sub.Star. AFAIK she didn't really lose anything with it, in fact, I think she's making more money now than before.
Last I recall, Fen was afraid of moving over because he has a team under his wing and doesn't want to put their "employment" at risk. The way I see it the benefits far outweighs the cons and I highly doubt Patreon is going to stop at just a few particular fetishes. Give it time and they may just ban porn entirely.